Modulation of ejector pumps to provide uniform and controllable ejector speed during ejector stroke for articulated trucks and the like having ejector type dump mechanism

ABSTRACT

A material eject system includes an ejector mounted to a bed of a vehicle which is movable between a rear end and a forward end of the bed for ejecting material from the bed. The ejector is powered by a cylinder having different fluid volumes depending on the direction of motion of the cylinder. A control circuit operates with the ejector motor to automatically move the ejector through eject and return cycles. Further, the control circuit detects different positions of the cylinder and automatically operates the cylinder at different speeds to maintain a constant motor and ejector speed throughout the material eject cycle.

TECHNICAL FIELD

[0001] The present invention relates generally to articulated trucks andmore particularly, to articulated trucks having a bed for carryingmaterial therein.

BACKGROUND OF THE INVENTION

[0002] Dump trucks have long been known in the art, for use in carryingdifferent types of loads. One such use is in the construction industryfor carrying dirt or other construction materials in the dump truck bed.A typical dump truck bed includes a tailgate defining a rear wall of thetruck bed. The tailgate retains the material within the bed when thetailgate is in a storage or raised position and permits material to beejected from the bed as the dump truck bed is raised. U.S. Pat. No.5,456,521, assigned to the assignee of the present invention, disclosesan unloading gate for a dump truck wherein the gate is mounted to one ormore rails disposed on the bottom surface of the bed. The unloading gatemoves from one end of the bed to the other to scrape and clean the bedafter unloading or dumping of the material. The unloading gate in thispatent is utilized in conjunction with a conventional dump truck bedwhich lifts at its forward end closest to the tractor cab and utilizesgravity to dump the material from the dump truck bed.

[0003] Applicant has had under development a new material carryingvehicle with a new material ejection system as is described in U.S.patent application Ser. No. 09/160,698, filed Sep. 25, 1998, entitled‘Hydraulic System For a Work Machine Having an Ejector Cylinder and aTailgate Cylinder’, assigned to the assignee of the present invention,which is hereby incorporated in its entirety herein. A variation of theabove system is disclosed in U.S. patent application Ser. No.08/936,128, filed Sep. 24, 1997, entitled ‘Tailgate Latching Mechanism’,assigned to the assignee of the present invention, and herebyincorporated in its entirety herein.

[0004] Such a material eject system has a motor, for example, ahydraulic cylinder, that is connected to an ejector blade having a homeposition at the front end of the bed. To initiate a material ejectoperation, the motor moves the ejector blade toward the rear of thevehicle, thereby pushing the material in the bed off of the rear edge ofthe bed. The ejector blade is then retracted or returned to its homeposition at the front of the bed. The bed normally includes a tailgatewhich prevents material from exiting the bed while the material is beingtransported. During the material eject cycle, the tailgate is movedbetween its closed and open positions in synchronization with theoperation of the ejector blade.

[0005] A vehicle having a material eject system has several advantagesover traditional dump trucks. For example, the vehicle bed is notraised; and its center of gravity is not elevated as the material isbeing ejected. Therefore, vehicle stability is not adversely affected bythe material ejection process. By maintaining a lower center of gravity,a material ejection system is more suitable for controlled spreading ofthe material during the ejection process. Further, by not raising thebed, the vehicle is not exposed to overhead obstacles such as trees andpower lines. In addition, the profile of the ejector blade closelymatches the cross-sectional profile of the bed and therefore,substantially all of the material in the bed is scraped out of the bedduring the ejection process. Thus, a vehicle material ejection system isgenerally more efficient and flexible than the traditional elevatingmaterial dumping systems.

[0006] The motor driving the ejector blade is normally a hydraulicmotor, for example, a multistage cylinder, that is supplied hydraulicfluid by a constant or fixed displacement pump being driven by thevehicle engine. Thus, the pump is supplying a fixed flow rate of fluidto the cylinder over the material eject cycle. The multistage cylinderis comprised of a plurality, for example, four nested telescopingcylinders of successively smaller diameters. During the material ejectcycle, the hydraulic fluid is supplied to the largest cylinder segmentwhich has the greatest volume. When that cylinder segment reaches theend of its stroke, the hydraulic fluid is supplied to a second smallercylinder segment which has a smaller volume. Thus, the constantdisplacement pump will fill the second smaller cylinder segment in lesstime than it took to fill the first larger cylinder segment; and thesecond cylinder segment will extend at a faster speed than the firstlarger cylinder segment. That process continues with the extension ofeach successively smaller cylinder segment until the cylinder is fullyextended. With each successively smaller cylinder segment, the smallercylinder volume produces a greater speed of extension. Thus, as theejector blade moves through the material eject cycle, the velocity ofthe ejector blade continuously increases. That increasing velocity ofthe ejector blade increases the rate at which material is ejected fromthe bed, thereby creating a nonuniformity in how the material is beingspread as it is being ejected. Thus, there is a need to drive theejector blade at a constant velocity throughout the material ejectstroke in order to eject the material from the bed at a constant rate.

DISCLOSURE OF THE INVENTION

[0007] The present invention overcomes the foregoing and othershortcomings and drawbacks of material ejecting systems and methods ofmaterial ejecting heretofore known. While the invention will bedescribed in connection with certain embodiments, it will be understoodthat the invention is not limited to these embodiments. On the contrary,the invention includes all alternatives, modifications and equivalentsas may be included within the spirit and scope of the present invention.

[0008] In accordance with one embodiment of the present invention, amaterial eject system for ejecting material from a bed of a vehicletransporting the material has an ejector mounted to the bed of thevehicle which is movable between a forward end of the bed and a rear endof the bed. A motor is mechanically connected to the ejector and movesthe ejector through an ejector stroke to dispense material from the bed.The motor, in response to a constant input, operates at a first speedduring a first portion of the ejector stroke and operates at a secondspeed during a second portion of the ejector stroke. A speed control isoperatively connected to the motor and automatically changes the inputto the motor to operate the motor at the first speed during the secondportion of the ejector stroke. Thus, by maintaining a constant motorspeed, the ejector blade speed is moved at a constant velocitythroughout the eject stroke and the layer depth of material beingejected is also constant.

[0009] Another embodiment of the invention is a method of a method ofcontrolling an operation of a motor mechanically connected to an ejectoroperatively mounted on a bed of a vehicle. The bed contains materialbeing transported by the vehicle. The method first moves the vehicle ata vehicle speed, and thereafter, simultaneously moves the ejectorthrough an eject stroke at one of a plurality of selectable ejectorspeeds to eject the material from the bed of the moving vehicle anddeposit the material in a layer.

[0010] The above and other objects, features and advantages of thepresent invention will become apparent from the following descriptionand the attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0011] For a better understanding of the present invention, referencemay be made to the accompanying drawings in which:

[0012]FIG. 1 is a side elevation view of a vehicle including a trailerincorporating an ejector system in accordance with the principles of thepresent invention.

[0013]FIG. 2 is a partial cross-sectional elevation of the trailerillustrating the operation of the ejector system in accordance with theprinciples of the present invention.

[0014]FIG. 3 is a schematic block diagram of an electrical and hydrauliccontrol system for operating the ejector system in accordance with theprinciples of the present invention.

[0015]FIG. 4 is a schematic block diagram of further details of thehydraulic control system illustrated in FIG. 3.

[0016]FIG. 5 is a schematic block diagram of an alternative embodimentof the electrical control system illustrated in FIG. 3.

[0017]FIG. 6 is a flow chart illustrating the steps of a shuffle cycleimplemented with the material eject control system of FIG. 5 inaccordance with the principles of the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

[0018] Referring to FIG. 1, an articulated truck 20 includes a tractor22 and a trailer 24 having a material carrying bed or receptacle 26mounted on a frame 28. The bed 26 includes a bottom 30 and a pair ofgenerally upright, spaced apart and parallel side walls 32. The bed 26further includes a tailgate 34 pivotable at its bottom edge with respectto a rear edge 36 of the bottom 30. One of a pair of guide rails 38 ismounted at the top edge of each of the side walls 32. The guide rails 38may be integrally formed as part of the side walls 30 or may be separatecomponents, for example, a metal I-beam, attached to the side walls in aknown manner.

[0019] A material ejection system 40 is disposed within the bed 26 andis slidably movable along the guide rails 38 between the side walls 32.The ejection system 40 includes an ejector in the form of a blade orplate 42 forming a forward wall of the bed 26 and extending essentiallythe entire width of the bed 26 from a position above the side walls 32to the bottom 30. The ejector blade 42 preferably has a profilesubstantially matching the cross-sectional profile of the bed 26. Theejector blade 42 includes a pair of guide member assemblies 44 thatinclude guide rollers for controlling the motion of the ejector blade 42along the guide rails 38. The ejector blade 42 further rides on one ormore support wheels 46 which are normally carried along the bottom edgeof the ejector blade 42 and ride on the bottom 30 of the bed 26. Thevehicle 20 is configured to carry loads for earth moving operations, forexample, loads of dirt, rock, gravel and other similar materials.

[0020] The material ejection system 40 further includes a drivemechanism or motor 48, for example, a multistage cylinder 49, which ispowered by an ejector pump 53 mechanically driven by the vehicle engine54. As shown in FIG. 3, the ejector pump 53 pumps hydraulic fluid from afluid source or tank 56 functioning as a reservoir or sump, through anejector flow control valve, for example, a multiposition selector valve58, to the multistage ejector cylinder 49. The multistage cylinder 49 iscomprised of three cylinder segments 50-52 which operate sequentially.The largest cylinder segment 50 is rigidly connected to the back of theejector blade 42, and the rod 57 from the smallest cylinder segment 52is pivotally connected to a frame member adjacent the front of the bed26.

[0021] Referring to FIGS. 2 and 3, the ejector blade 42 is initially atits home position 47 as shown in phantom in FIG. 2. The ejector pump 53is a fixed displacement, high capacity pump that pumps hydraulic fluidor oil into the larger, full end port 60 of the largest segment 50 ofthe multistage cylinder 49. The largest segment has the largest capacityto accept hydraulic oil and extends fully prior to the smaller,intermediate cylinder segment 51 beginning to operate. After theintermediate cylinder segment 51 is fully extended, the smallestcylinder segment 52 begins to extend. When the three cylinder segments50-52 are fully extended, the ejector blade 42 has been moved from itshome position 47 at the front end of the bed 26 to its fully extendedposition 55 at the rear end 36 of the bed 26. To return the ejectorblade 42, hydraulic fluid is introduced into the smaller, annular endport 62 in the smallest cylinder segment 52 to collapse the cylinder 49back to its unextended or retracted configuration.

[0022] The volume of fluid necessary to fully return the ejector blade42 is up to an order of magnitude less than the volume of fluid used toextend the cylinder. Using the ejector pump 53 to retract the cylindermay overwork the cylinder seals and heat the oil being exhausted, fromthe full end port 60. That cylinder operation is inefficient andpotentially damaging to the cylinder. To alleviate that problem, thematerial ejection system 40 includes a second, return pump 64 alsodriven by the vehicle engine 54. The return pump 64 is a substantiallysmaller pump and has a smaller flow rate, for example, 16 cc/min, thanthe ejector pump which, for example, has a flow rate of 160 cc/min.Therefore, with the present invention, the ejector pump 53 suppliesfluid to the high volume, larger end port 60, and the return pump 64 isused to supply fluid to the low volume, smaller, annular end port 62 topower motion of the ejector blade 42 during its return cycle or stroke.

[0023] Referring to FIGS. 3 and 4, the ejector valve 58 is operated bypilot solenoids 66, 67 which provide hydraulic fluid at pilot pressuresto move the main valve spool 68 to one of four stages or statesrepresenting different flows of hydraulic fluid through the valve 58.The ejector valve 58 is a known four ‘stage’ valve commerciallyavailable from Caterpillar Belgium SA, located at Gosselies, Belgium, aspart number 139-5823, directly pertaining to a control valve Gp.Alternatively, other four ‘stage’ valves, or four position valves arecommercially available from other vendors and may require actuation byassociated solenoids. The ejector valve 58 has a first pressure port 70connected to an output of the ejector pump 53 via pressure line 76 and asecond port 71 connected to the tank 56 via tank line 78. The ejectorvalve 58 further has a third port 72 connected to an eject pressure line80 that in turn is connected to the larger end port 60 on the cylinder49. A fourth port 73 is connected to the smaller end port 62 via thereturn valve 84. Upon the pilot solenoids 66, 67 receiving a command toinitiate a material eject cycle or stroke, the valve 58 moves an ejectstage 82 of the spool 68 in to fluid communication with the pressure andtank lines 76, 78, respectively. Thus, high pressure hydraulic fluidpasses through first and third ports 70, 72 of the ejector valve 58,through line 82 and into the port 60 of the multistage cylinder 58. Asthe cylinder 58 extends to move the ejector blade 42 toward the rear end36 of the bed 26, hydraulic oil is discharged from the cylinder smallerend port 62. The oil then returns to the tank 56 via a return valve 84and ports 73, 71 of the ejector valve 58.

[0024] The return valve 84 is a two stage valve that facilitates the useof the return pump 64 and has a first pressure port 85 connected to anoutput of the return pump 64 and a second port 86 connected to the tank56 via the ejector valve 58. The return valve further has a third port87 tied to the port 86 and a fourth port 88 connected to the smallerport 62 of the cylinder 58. During the eject cycle, the return valvedirects the output from the return pump 64 to tank via ports 73, 71 ofthe ejector valve 58.

[0025] Upon receiving a command to initiate a return stroke, the pilotsolenoids 66, 67 switch the spool 68 of the ejector valve 58 to connectthe return stage 90 to the fluid pressure and tank fluid paths 76, 78.That action disconnects the pressure line 76 from the ejector pump 53from the cylinder port 60. In addition, the return valve 84 isenergized, thereby placing the return pump 66 into fluid communicationwith the ejector cylinder 50. The return pump 60 having a smaller fixeddisplacement than the ejector pump 53, provides hydraulic fluid throughthe return valve 84 via the first and fourth ports 85, 88, respectively,through the return pressure line 92 to the cylinder smaller volume port62. As the multistage cylinder 58 returns to its retracted position,hydraulic oil is discharged from the larger volume port 60 through theline 80 and back to tank 56 via the respective third and second ports72, 71 of the ejector valve 58. The smaller displacement return pump 64better matches the capability of the smallest cylinder segment 52 toreceive the hydraulic fluid and not overwork the cylinder. Thus, theejector blade 42 is reliably moved through the return stroke to its homeposition 47.

[0026] While the material ejection system 40 may be operated manually toinitiate the material eject and return cycles of the ejector blade 42,it is preferable that the ejection mechanism 40 after initiation of aneject cycle provide a fully automatic cycle to move the ejector blade 42from the home position 47 to the fully extended position 55 and thenreturn back to the home position 47 without operator intervention. Thematerial ejection system 40 includes a control circuit 100 (FIG. 3) thateffectively provides the desired automatic cycle of operation of theejector blade 42.

[0027] When power is initially applied to the control system 100 byactivating an ignition switch 110, inputs to a pulse width modulator(‘PWM’) generator 111 reset the PWM generator 111 to its default state.In its default state, the PWM generator 111 provides outputs to theejector valve 58 commanding the pilot solenoids 66, 67 to move the holdstage 98 of the spool 68 in fluid communication with the pressure andtank lines 76, 78, respectively. In the hold stage, the output ports 72,73 are blocked, thereby blocking the flow of hydraulic fluid to and fromthe ejector cylinder 49 and blocking the ejector cylinder in its presentposition, for example, the home position. Hydraulic fluid from theejector pump 53 is dumped to a brake cooling line 94 via a pressureregulator 96 within the ejector valve 58.

[0028] An eject push button 102 is connected to the vehicle battery 104via normally closed contacts of a stop push button 106, normally closedcontacts of a return line fluid pressure sensor or switch 108 andignition switch 110. Upon the operator depressing the eject pushbutton.102, power is supplied to a relay coil RLB switching the state ofthe RLB relay contacts 112, 113. Circuitry is provided in a known mannerto latch relay coil RLB via latch line 114 to power line 115 from thenormally closed contacts 128 of relay RLA. Changing the state of relaycontacts 112 changes the input to a pulse width modulator (‘PWM’)generator 111. The PWM generator 111 then provides output signals to theejector valve 58 commanding the solenoids 66, 67 to move the eject stage82 of the spool 68 in fluid communication with the pressure and tanklines 76, 78. With the eject stage 82 of the spool 68 connected to thesupply and tank lines 76, 78, the cylinder 49 is driven from its homeposition 77 toward its fully extended position 55 in a manner aspreviously described.

[0029] Upon the RLB contacts 113 switching state, power is supplied toan eject LED 116 to provide a visual indication that the eject cycle isactive. Switching the state of the RLB contacts 113 also energizes thesolenoid 117 to switch the state of gate valve 118. High pressurehydraulic fluid is supplied over line 80 to gate cylinders 120.Hydraulic fluid is also discharged from the gate cylinders 120 throughthe gate valve 118, through flow restrictor 122 (FIG. 4) and back to thetank 56. The flow restrictor 122 regulates the rate at which thecylinders 120 open the gate 34. It is desired that the operation of thegate 34 and the ejection of the material from the bed be coordinated andthat the material initially be ejected off of the gate. Therefore, thegate moves at a controlled rate from a closed position to a generallyhorizontal position in the time it takes the first cylinder segment 50to fully extend. Material is first ejected from the bed 26 when the gate34 is at its horizontal position, and thereafter, the gate 34 moves atthe same controlled rate until it is fully opened.

[0030] When the cylinder 58 moves to its fully extended position 55(FIG. 2), flow of hydraulic fluid in the eject line 80 ceases and theline pressure rapidly increases. An eject line fluid pressure sensor orswitch 124 is set to detect a high eject line pressure that is slightlybelow the pressure detected by pressure regulator 96 (FIG. 4). Whenpressure in the eject line 80 reaches the pressure limit of eject linepressure switch 124, the contacts 125 within eject line pressure switch124 close, thereby energizing relay coil (RLA). Circuitry (not shown) isprovided in the known manner to latch relay coil RLA via line 126 topower line 127. Upon the eject line pressure switch 124 energizing coilRLA, coil contacts 128 switch state to remove power from power line 115and the latch line 113 of relay coil RLB. De-energizing coil RLBswitches RLB contacts 112, 113 to their original state, therebyextinguishing the eject LED 116 and switching the input to the PWMgenerator 111 and the ejector valve 58 to their default states.

[0031] Switching of the RLA contacts 128 to their normally opened stateilluminates the return LED 132. Further, power is supplied to thesolenoid 134 (FIG. 3) of the return valve 84, thereby connecting thereturn stage 136 with the return valve ports 85-88. Energizing the RLArelay coil further switches the RLA contacts 130 which changes the inputstate of the PWM generator 111 so that the PWM generator 111 providessignals to the pilot solenoids 66, 90 of the ejector valve 58 to movethe return stage 90 of the spool 68 in fluid communication with thepressure and tank lines 76, 78. Thus, in a manner as previouslydescribed, the return pump 64 provides hydraulic fluid to the smallerend port 62 of the cylinder 58, thereby moving the cylinder 58 andejector blade 42 through a return stroke back from the fully extendedposition 55 toward the home position 47.

[0032] As the ejector blade 42 moves toward the home position 55, itpasses a tailgate proximity switch 142, thereby causing electricalcontacts within the proximity switch to close. The switch 142 is locateda sufficient distance from the home position 47 so as to allow the tailgate to close during the remaining return stroke of the ejector blade42. A distance of approximately 18 inches from the home position hasbeen found to be adequate. Closing the contacts within the switch 142provides power to the solenoid 117 of the gate valve 118. Thepressurized hydraulic fluid in return pressure line 92 passes throughthe gate valve 118 and into the gate cylinders 120. The restrictor 122is not operative when the gate 34 is closing; and therefore, the gatemoves toward its closed position a full unrestricted speed.

[0033] When the cylinder 58 moves to its fully retracted, home position47 (FIG. 2), flow of hydraulic fluid in the return line 92 ceases andthe line pressure rapidly increases. When pressure in the return line 92reaches the pressure limit of the return line pressure switch 108, thecontacts 142 within return line pressure switch 108 open, therebyremoving power from line 127 and relay coil RLA latch line 126. Relaycoil RLA is thus de-energized, and contacts 128, 130 are switched backto their normally closed states. The PWA generator 111 provides outputsignals to the ejector valve 58 commanding the pilot solenoids 66, 67 tomove the hold stage 98 of the spool 68 in fluid communication with thepressure and tank lines 76, 78, respectively. Hydraulic pressure isblocked at its current state in the cylinders 49, 120, and pressure fromthe ejector pump 53 is dumped to the brake cooling system through thepressure regulator valve 96. Thus, by the operator pushing the eject PB102, the ejector blade 42 is moved through a complete material ejectcycle by which the ejector blade 44 is first, advanced to the fullyextended position 55 at the rear edge 36 of the bed 26 and thereafter,automatically retracted to its home position.

[0034] The arrival of the ejector blade 42 at the home position isdetected by normally closed contacts of a home position proximity switch144 changing state. The normally closed contacts within the proximityswitch 144 maintain a relay coil RLC energized which maintains thenormally open RLC contacts 146 closed. The common terminal 148 of thecontacts 146 is connected through the normally closed contacts 113 andthe normally closed contacts 128 to the power line 127. Therefore, thestop LED 150 provides a visual indication that the ejector blade 42 isstopped whenever the relay coils RLA and RLB are de-energized. If uponeither of the coils RLA, RLB being activated, the stop LED isextinguished. When the ejector blade 42 reaches the home position andopens the contacts of the switch 144, the relay coil RLC isde-eneregized, and the contacts 146 switch to the normally closed state.Thus, the stop LED 150 is inoperable and power is supplied to thesuspension switch 152.

[0035] The above control circuit 100 includes an obstacle detectioncapability in that if the ejector blade 42 is moving in the materialeject stroke and encounters an obstacle or otherwise jams, the pressurewithin the eject line 80 will increase until the limit of the eject linepressure switch 124 is reached, thereby closing contacts 125. Aspreviously discussed, closing contacts 125 will automatically switch thedirection of motion of the ejector blade 42 and return it to the homeposition. Similarly, if during the return stroke of the ejector blade42, an obstacle or jam is encountered, the pressure in the return line92 will rapidly increase. When the pressure reaches the limit of thereturn line pressure switch 108, contacts 138 will open, therebyswitching the ejector valve 58 to the hold stage and freezing theejector blade 42 and tailgate 34 in their current positions.

[0036] It should also be noted that while the control circuit 100 forthe material eject system 40 provides an automatic cycle of operationfor the ejector blade 42, the operator at any time may override theautomatic cycle. For example, the operator at any time may actuate thereturn push button 140 which will immediately cause the eject cycle tobe terminated and the return cycle to be initiated. Further, theoperator at any time may depress the stop push button 106 which removespower from the control, thereby switching the PWM generator 111 and theejector valve 58 to their default states. The default state activatesthe hold stage 98 of the spool 68 and freezes the ejector blade 42 andtailgate 34 at their current positions.

[0037] As previously mentioned, one advantage of a vehicle with thematerial ejection system 40 described herein is that the load in the bedmay be spread over a large area by driving the vehicle during thematerial eject cycle. The thickness of the material layer spread willvary with the velocity of the vehicle 20 as well as the velocity of theejector blade 42. Considering the normally rugged terrain over which thematerial is being spread, the range of vehicle velocities is strictlylimited; and preferably, the vehicle should be driven at a constantspeed during the spreading operation. Therefore, the capability of beingable to select the speed at which the ejector blade moves is highlydesirable. The ejector valve 58 has the capability of moving the spool68 such that flow is regulated through the ports 70-73. For example,with the eject stage 82 connected to the ports 70-73, the spool positioncan be further regulated with the pilot solenoids 66, 67 to change thespool position such that the flow paths through the spool 68 arepartially blocked. Further, the extent of fluid flow through the valve58 can be controlled reasonably accurately and repeatably with the pilotsolenoids 66, 67. The control circuit 100 further includes a speedcontrol 154 that includes in part a variable resistance 156 that isswitched across inputs of the PWM generator 111 upon the RLB contacts112 being switched to their normally open state. The variable resistance156 is then used to change the input to the PWM generator 111 which inturn changes the operation of the pilot solenoids 66, 67 to regulate theoperation of the ejector valve 58. Thus, the speed control 154 can beused to provide less than full flow rate through the eject stage 82 ofthe spool 68. Further, the variable resistor 156 can be roughlycalibrated to the desired thickness of the layer of material to bespread during the material eject cycle while the vehicle is moving aknown constant speed. By providing an operator adjustable speed control,not only is material automatically ejected from the vehicle withoutoperator intervention, but the operator may preselect the desired depthor layer thickness of material to be spread. Further, the entire cyclefunctions automatically and the attention of the operator can be focusedon driving the vehicle.

[0038] The fixed displacement ejector pump 53 supplies a fixed flow rateof fluid, and at the beginning of the material eject stroke, the ejectorcylinder 49 receives fluid into its largest cylinder segment 50. Whenthe first cylinder segment 50 is fully extended, the second cylindersegment 51 receives the same constant rate of fluid into a smallervolume resulting in a faster speed of extension for the second cylindersegment 51. Thus, the ejector blade 42 is moved at a higher velocitythan was provided by the first cylinder segment 50. Similarly, at theend of the stroke of the second cylinder segment 51, the third cylindersegment 52 having an even smaller volume is moved at a higher velocity.Thus, as the ejector cylinder 49 is extended through the ejector stroke,it will be extended at an ever increasing velocity with the activationof each of the successively smaller cylinder segment 51, 52.

[0039] In static ejection applications, the variation of velocity of theejector blade 42 is of no consequence. However, in material spreadingapplications where the vehicle is moving simultaneously with the ejectstroke, variations in the velocity of the ejector blade 42 causes avariation in the thickness of the material being spread. Referring toFIG. 3, the speed control 154 is utilized to modulate the ejector valve58 and provide different flow rates to the ejector cylinder 49 thataccount for the smaller piston area with each successive cylindersegment.

[0040] To initiate a variation in the flow rate of fluid through theejector valve 58, the activation of each successive cylinder segment 51,52 must be detected. That may be done in one of several ways. First,proximity sensors 160-162 may be utilized to detect the end of eachpiston stroke in each cylinder segment 50-52. The output of theproximity sensors 160-162 is provided to the speed control 154 whichprovides either a resistance value or a voltage level on the inputs ofthe pulse with PWM generator 111. The PWM generator then controls thepilot solenoids 66, 67 to position the spool 68 within the ejector valve58 to provide a flow rate through the ejector valve corresponding to thecurrently active cylinder segment. In other words, when proximity switch160 detects that the piston in the largest cylinder segment 50 is at theend of its stroke, the speed regulator 154 provides a new resistance tothe PWM generator 111 to slightly change the position of the spool 68.The ejector valve 58 changes the position of the spool 68 to adjust orreduce the flow rate of fluid for the successive smaller cylindersegment 51. The flow through the valve 58 is reduced to cause the pistonin the second cylinder segment 51 to move the ejector blade 42 at avelocity approximately equal to the velocity imparted by the previouslarger cylinder segment 50. The flow is further reduced when proximityswitch detects that the piston in the cylinder segment 51 is at the endof its stroke. Thus, by changing the flow rate through the ejector valve58, the ejector blade 42 is moved at a constant velocity throughout thematerial eject stroke. Moving the ejector blade 42 at a constantvelocity, greatly enhances the ability of the vehicle to spread auniform thickness of material during the eject cycle.

[0041] Referring to FIG. 5, an alternative embodiment of the materialejection system 40 is illustrated. Instead of the discreet componentsdescribed with respect to FIG. 3, the control system 100 of FIG. 5utilizes a logic controller, for example, a programmable logiccontroller, 170. In a known manner, the various push buttons 102, 106,140, proximity switches 142, 144, pressure switches 108, 124 and othercomponents providing input state signals are provided to inputs of thelogic controller 170. The logic controller is provided with an internallogic network, preferably a programmable network, such that various setsof output signal states are provided in response to different sets ofinput signal states.

[0042] In certain applications in which the material being ejected is astickier material, for example, a clay-like material, at the end of theejection stroke, a bridge of material may form between the side walls 32of the bed 26 and the ejector blade 42. The bridge of material oftensimply sticks to and hangs from the ejector blade 42 without droppingfrom the bed 26. In that event, when the ejector blade returns to thehome position, the bridging material is carried back into the bed 26. Toalleviate that problem, a shuffle-cycle is used in which the ejectorblade 42, after reaching the end 55 of the eject stroke, is retracted ashort fixed distance into the bed to break the bridge of material. Afterbreaking the bridge of material, the material generally falls to thebottom 30 of the bed; and the ejector blade is switched into the ejectcycle to push the material from the bed. Normally, only a single shuffleof the ejector blade 42 is required to dislodge the bridging material.If for some reason the dislodged material causes an obstruction or jamof the ejector blade 42 during the eject portion of the shuffle cycle,the ejector blade 42 will provide a smaller shuffle cycle, that is,retracting a short distance and then switching back to the eject mode.If the obstruction is again encountered, the ejector blade eitherreturns to home or is switched to the hold cycle as previouslydescribed.

[0043] Such a shuffle cycle is illustrated in the flow chart of FIG. 6which represents a material ejection cycle implemented with the logiccontroller 170 of FIG. 5. If the material being moved is a stickyclay-like material, the operator will have turned on the shuffle switch172. The material eject cycle begins by detecting at 200 of FIG. 6 thestate of the stop push button 106. If the stop push button 106 ispushed, the logic controller 170 provides outputs to the PWM generator111 to control the pilot solenoid 66, 67 to move the hold stage 98 ofthe spool 68 in communication with the pressure and tank lines 76, 78.If the stop push button 106 is not depressed, the logic controller 170then at 204 determines the state of the eject push button 102. If theeject push button 102 has been depressed, the logic controller 170 at206 initiates the eject and gate open cycles. Again, the PWM generator111 is providing input signals that cause the pilot solenoid 66, 67 tomove the eject stage 82 of the spool 68 of the valve 58 in communicationwith fluid lines 76, 78, thereby providing fluid to the eject cylinder49 and moving the ejector blade 42 through the material eject cycle.Simultaneously, the logic controller 170 provides an output signal tosolenoid 117 of gate valve 118 which permits the flow of pressurizedfluid through the gate cylinders 120 to begin opening the gate 34.During the material eject stroke, the logic controller 170 iscontinuously checking the state of the pressure switch 124 in the ejectline 80. Assuming no obstructions are encountered during the materialeject cycle and no other push buttons are actuated, the logic controller170 continuously moves through the flow chart of FIG. 6 until the ejectline pressure switch 124 closes its contacts 125 in response to theejector cylinder 49 reaching the end of the eject stroke.

[0044] The logic controller 170 detects at 208 the eject line pressureswitch 124 closing in response to the cylinder 58 reaching the end ofits stroke. Further, the logic controller 170 detects at 210 that theshuffle cycle has been activated but further detects at 212 that theshuffle B flag is not set. Thereafter, the logic controller at 214initiates the return cycle by providing inputs to the PWM generator 111to control the pilot solenoids 66, 67 to move the return stage 90 of thespool 68 of the ejector valve 58 in fluid communication with pressureand tank lines 76, 78, respectively. The logic controller 170 then againdetects that the shuffle cycle is on at 215; and at 216, the controllerdetects that the shuffle A flag is set. The shuffle A flag was set at217 by a prior off state of the shuffle switch 172. At 218, thecontroller 170 starts the shuffle A timer which controls the length ofthe retraction of the ejector blade during the shuffle cycle. While theshuffle timer is timing, the logic controller continues to move theejector blade 42 toward the home position testing for whether the returnline pressure switch 108 is activated. Assuming no obstruction isencountered, the logic controller at 220 then detects that the shuffle Atimer has timed out and at 222 resets the shuffle A flag and sets the Bflag. The logic controller then at 206 again initiates the eject cycle,thereby reversing the motion of the ejector blade 42 after a shortreturn stroke determined by the length of timer A.

[0045] Presumably, during the retract cycle, any bridge of stickymaterial between the ejector blade 42 and side walls 32 of the bed 36has been broken; and the material has dropped to the bottom 30 of thebed 26. Thus, during the eject stroke, the bridging material is pushedby the ejector blade 42 from the bed. When the logic controller 170detects at 208 that an eject pressure limit has been reached, the ejectpressure limit may be caused either by the ejector blade 42 achievingthe end of the ejection cycle or the ejector blade 42 encountering anobstruction. The logic controller 170 detects at 210 that the shufflecycle is on and, at 212, that the shuffle B flag is set. Thereafter, at224, the logic controller then starts the shuffle B timer and resets theshuffle B flag. The logic controller at 214 initiates a return cycle,and the ejector blade 42 retracts a short distance for a period of timedetermined by the length of the shuffle B timer. When the logiccontroller at 226 detects the shuffle B timer has expired, the ejectcycle is again initiated at 206. At this time, all of the shuffle flagshave been reset; and therefore, when the eject line pressure switchdetects the pressure limit, the logic controller 170 initiates a returnof the ejector blade 42 back to the home position.

[0046] If the logic controller 170 at 228 detects the return linepressure switch sensing a pressure limit, the PWM generator 111 commandsthe pilot solenoid 66, 67 to move the ejector valve to the hold stage.If no obstruction is detected by the return line pressure switch, thelogic controller 170 at 230 detects when the ejector blade 42 moves pastthe tailgate proximity switch 142. At that point, the logic controller170 initiates at 232 a gate closing cycle by providing an output to thesolenoid 117 of the gate valve 118, thereby permitting the pressurizedfluid to move through the gate cylinders 120 in a direction causing thegate 34 to close. When the ejector blade 42 reaches the home position,the return line pressure switch again produces a pressure limit signalwhich is detected at 228 by the logic controller 170; and thereafter,the logic controller 170 at 202 initiates the hold cycle.

[0047] While not specifically shown, it will be appreciated that otherconstructions of the material eject system may be used without departingfrom the spirit and scope of the present invention. For example, in thedisclosed embodiment, the operation of the material eject mechanism 40is initiated by push buttons and other switches. As will be appreciatedother types of operator controls may be utilized such as joysticks,levers, remote controls, etc. Further, the operation of the differentcylinder segments 50-52 are detected by proximity switches 160-162. Asthe multistage cylinder 49 shifts from one cylinder element to another,for example, from cylinder segment 50 to cylinder segment 51, thehydraulic pressure in the eject pressure line 80 experiences a rapidchange. That rapid change can be detected by other pressure switches orby a pressure sensor providing an input to the logic controller 170.Upon detecting the changes in pressure representing a transition betweenthe cylinder segments, command signals can be provided to the pilotsolenoid 66, 67 to modulate the ejector valve 58 and provide a differentflow rate to the ejector cylinder 50. Thus, the detection of variationsin pressure in the eject line 80 can be used instead of the proximityswitches 160-162 to detect operational transitions between the cylindersegments 50-52. Further, the multistage cylinder speed control describedherein may be used with such cylinders in other applications than theone disclosed herein.

[0048] As will be appreciated, in a further alternative embodiment, theconstant displacement ejector pump 53 can be replaced by a variabledisplacement pump. The flow rate from the pump can be controlled tomatch the difference in flows associated with the various cylindersegments 50-52 in order to move the ejector blade 42 at a constant speedthroughout the material eject cycle. Alternatively, in static ejectapplications where the material is not being spread, the speed control154 can be disabled, so that the ejector blade moves through the ejectstroke at the greatest possible speed, thereby providing the shortestpossible and most efficient material eject cycle.

[0049] In a further embodiment, the motor 48 for the ejector blade 42may be a hybrid combination of electric and hydraulic motors.

[0050] Industrial Applicability

[0051] With reference to the drawings and in operation, the materialejection control system 40 utilizes two pumps: a large capacity pump 53to extend the cylinder 49 in a material eject cycle, and a substantiallysmaller capacity pump 64 to retract the cylinder in an ejector bladereturn cycle. The smaller pump 64 provides a fluid supply that bettermatches the relatively small volume fluid required to retract thecylinder. Thus, the ejector return cycle operates more reliably.

[0052] The material ejection system 40 includes control circuitry 100for automatically controlling a full material ejection process whichincludes both a material eject stroke and a return stroke of the ejectorblade 42. The automated material ejection process has severaladvantages. First, it permits the operator to concentrate on driving thevehicle while the material ejection process is being executed. Second,it prevents the ejector blade 42 from being left in a position close tobut not at the home position. If the blade 42 is not fully retracted,material being loaded can be dumped forward of the ejector blade 42 ontothe ejector motor 48 during a material loading process. Dumping materialon the ejector motor 48 and associated system components exposes thosecomponents to damage.

[0053] The automatic ejection cycle is also sensitive to the ejectorblade 42 contacting obstacles and becoming jammed in either the ejectcycle or the return cycle. If an obstruction is encountered in the ejectcycle, the ejector blade 42 returns to the home position. If anobstruction is encountered in the return cycle, the ejector blade 42 isstopped. Thus, with the automatic cycle, the ejector motor 48 isprotected from repetitive attempts to clear an obstruction which maylead to overheating and damage to the ejector motor 48.

[0054] The vehicle ejection system 40 has the advantage of being able toeject material from the bed while the vehicle is moving withoutjeopardizing the stability of the vehicle 20. Further, since the ejectorblade 42 is motor driven, the ejection of material is a reliablecontinuous, uniform and generally repeatable operation. The controlcircuit 100 of the material ejection system 40 includes a speed control154 that permits the operator to select different speeds for the ejectorblade 42. By moving the ejector blade 42 at different speeds, if thevehicle is operating at a constant speed, material can be ejected fromthe vehicle and spread in layers of uniform but different thicknesses.Thus, the present invention has the advantage of permitting the operatorto select a desired thickness for a layer of material to be spread,initiate a material eject cycle and then fully concentrate on drivingthe vehicle 20 at a fixed speed knowing the material will beautomatically ejected at the desired rate to achieve the desired layerthickness.

[0055] The disclosed multistage cylinder 49 moves the ejector blade 42by successively operating successively smaller cylinder segments 50-52.Those successively smaller cylinder segments 50-52 present respectivesuccessively smaller cylinder volumes to the fixed displacement ejectorpump 53. Thus, with a constant displacement pump, each successivecylinder segment 50-52 will move the ejector blade 42 at respectivesuccessively increasing speeds. The control circuit 100 detectsoperating transitions between the successive cylinder segments 50-52 andmodulates the ejector valve 58 so that hydraulic fluid is supplied tothe cylinder 49 at successively smaller flow rates. Consequently, theoperation of each cylinder segment 50-52 is adjusted so that the ejectorblade 42 moves at a constant speed throughout the material eject cycle.Thus, the speed of the ejector blade 42 is controlled and maintainedconstant in order to eject the material at a constant rate and maintaina uniform layer thickness as the material is being spread from themoving vehicle 20.

[0056] The control 100 further includes a shuffle cycle switch 172 whichis directed to ejecting any material that sticks between the ejectorblade 42 and the side walls 32 at the extended position 55 of theejector blade 42. When turned on, the shuffle cycle moves the ejectorblade 42 through a small return stroke in order to break the bridgingmaterial and then after, through a subsequent eject stroke to push thematerial from the bed 26. If in the shuffle ejection stroke anobstruction is encountered, the ejector blade 42 will again retract asmall distance and once again move into a material eject cycle to eitherclear the obstruction or eject the bridging material. Thus, the controlcircuit 100 permits the operator to automatically operate the ejectorblade 42 in a manner fully ejecting sticky materials that may be loadedinto the bed 26.

[0057] It should be noted that the ejector valve 58 has a float stage174 that may be moved into fluid communication with the pressure andtank lines 76, 78, respectively. With the ejector valve 58 switched tothe float mode, the ports 60, 62 of the ejector cylinder 49 are openedto the tank 26. This permits the ejector blade 42 to be mechanicallymoved without the application of hydraulic pressure for maintenance orother purposes.

[0058] Other aspects, objects and advantages of the present inventioncan be obtained from a study of the drawings, the disclosure and theappended claims.

What is claimed is:
 1. A material eject system for ejecting materialfrom a bed of a vehicle transporting the material, the material ejectsystem comprising: an ejector operatively associated with the bed of thevehicle and movable between a forward end of the bed and a rear end ofthe bed; a motor mechanically connected to the ejector for moving theejector through an ejector stroke to dispense material from the bed, themotor, in response to a constant input, operating at a first speedduring a first portion of the ejector stroke and operating at a secondspeed during a second portion of the ejector stroke; and a speed controloperatively connected to the motor and automatically changing the inputto the motor to operate the motor at the first speed during the secondportion of the ejector stroke.
 2. A material eject system for ejectingmaterial from a bed of a vehicle transporting the material, the materialeject system comprising: an ejector operatively associated with the bedof the vehicle and movable between a forward end of the bed and a rearend of the bed; a motor mechanically connected to the ejector for movingthe ejector through an ejector stroke to dispense material from the bed,the motor in response to a fixed input operating at a first speed duringa first portion of the ejector stroke and operating at a second speedduring a second portion of the ejector stroke; a sensor for sensing themotor moving the ejector from the first portion to the second portion ofthe eject cycle; a speed control operatively connected to the sensor andthe motor and changing the input to the motor in response to the sensordetecting the motor moving the ejector from the first portion to thesecond portion of the eject cycle to operate the motor at the firstspeed in the second portion of the eject cycle.
 3. A material ejectsystem of claim 2 wherein the motor is a fluid motor and the methodfurther comprises supplying fluid at a first flow rate to the fluidmotor to operate the motor at the first speed during the first portionof the eject cycle.
 4. A material eject system of claim 3 wherein avalve is in fluid communication with the fluid motor and the methodfurther comprises actuating the valve to supply fluid at a first flowrate to the fluid motor to operate the motor at the first speed duringthe first portion of the eject cycle.
 5. A method of controlling anoperation of a motor mechanically connected to an ejector operativelyassociated with a bed of a vehicle, the bed containing material beingtransported by the vehicle, the method comprising: providing a firstinput to the motor; operating the motor in response to the first inputat a first speed during a first portion of an ejector stroke of theejector, the motor operating at a second speed during a second portionof the ejector stroke in response to the first input; providing a secondinput to the motor different from the first input; and operating themotor in response to the second input at the first speed during thesecond portion of the ejector stroke of the ejector.
 6. method of claim5 further comprising detecting when the motor begins moving the ejectorthrough the second portion of the ejector stroke.
 7. method of claim 6further comprising providing the second input to the motor in responseto detecting when the motor begins moving the ejector through the secondportion of the ejector stroke.
 8. method of claim 6 wherein the motor isa fluid motor and the method further comprises supplying a first flowrate of fluid to the fluid motor to operate the motor at the first speedduring the first portion of the ejector stroke and the motor willoperate at a second speed in response to the first flow rate during thesecond portion of the eject stroke.
 9. A method of claim 8 wherein avalve is in fluid communication with the fluid motor and the methodfurther comprises actuating the valve to supply the fluid at the firstflow rate to the of fluid motor.
 10. A method of claim 9 furthercomprising detecting when the motor begins moving the ejector in thesecond portion of the eject stroke.
 11. A method of claim 10 furthercomprising actuating the valve to supply the fluid to the fluid motor ata second flow rate in response to detecting when the motor begins movingthe ejector in the second portion of the eject stroke so that the motormoves at the first speed during the second portion of the eject stroke.12. A method of claim 11 further comprising supplying command signals tothe valve to operate the valve and cause the first flow rate of fluid tobe supplied to the fluid motor during the first portion of the ejectstroke and the second flow rate of fluid to be supplied to the fluidmotor during the second portion of the eject stroke.
 13. A method ofcontrolling an operation of a motor mechanically connected to an ejectoroperatively mounted on a bed of a vehicle, the bed containing materialbeing transported by the vehicle, the method comprising: moving thevehicle at a vehicle speed; and simultaneously moving the ejectorthrough an eject stroke at one of a plurality of selectable ejectorspeeds to eject the material from the bed of the moving vehicle anddeposit the material in a layer.
 14. A method of claim 13 furthercomprising selecting one of the plurality of selectable ejector speedsto move the ejector through the ejector stroke at a speed to deposit thematerial in a layer having a desired thickness.
 15. A cylinder controlsystem, comprising: a fluid source; a fluid cylinder operativelyconnected to the fluid source, wherein the fluid cylinder, in responseto a constant fluid input from the fluid source, operates at a firstspeed during a first portion of an extension stroke and operates at asecond speed during a second portion of the extension stroke; and aspeed control operatively connected to the cylinder and automaticallychanging the fluid input to the cylinder to operate the cylinder at thefirst speed during the second portion of the extension stroke.
 16. Amethod of controlling operation of a fluid cylinder, comprising:providing a first fluid input to the cylinder; operating the cylinder inresponse to the first fluid input at a first speed during a firstportion of an extension stroke, the cylinder operating at a second speedduring a second portion of the extension stroke in response to the firstfluid input; providing a second fluid input to the cylinder differentfrom the first input; and operating the cylinder in response to thesecond fluid input at the first speed during the second portion of theextension stroke.
 17. A method of claim 16 further comprising detectingwhen the cylinder begins moving through the second portion of theextension stroke.
 18. A method of claim 17 further comprising providingthe second fluid input to the cylinder in response to detecting when thecylinder begins moving through the second portion of the extensionstroke.